Selectively rigidizable and actively steerable articulatable device

ABSTRACT

A selectively rigidizable and actively steerable device is described. In one aspect, an articulatable device is described that includes a flexible inner tube having a first lumen, a flexible outer tube that receives the inner tube, and a multiplicity of overlapping, rigidizable scale-like strips. Each scale-like strip is coupled with the inner tube and positioned between the inner and outer tubes. Of particular note, the overlapping strips are actuatable between a non-rigidized state in which overlapping strips are slideable relative to one another and a rigidized state in which overlapping strips are not slideable relative to one another.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. 119(e) from U.S.Provisional Patent Application No. 60/952,162 filed Jul. 26, 2007, whichis hereby incorporated by reference herein for all purposes.

FIELD OF THE INVENTION

The present invention generally relates to articulatable devices and,particularly, to articulatable devices that are selectively rigidizableand actively steerable.

BACKGROUND OF THE INVENTION

There are an increasing number of applications where articulatabledevices are desirable. By way of example, robotic arms having one ormore joints have been used in numerous manufacturing processes as wellas in more complex applications such as in outer space or forexploratory or investigative purposes in places where it may beimpossible, unsafe or undesirable for humans to go. Conventionalarticulatable arms and other devices are often heavy and even bulky as aresult of the device having to be strong or rigid enough to support notonly its own weight, especially as they become increasingly longer (andhence must support a greater bending moment), as well as the weight ofanything that the device may be carrying.

While existing devices may be suitable in specific applications, moremobile, configurable and lightweight articulatable devices aredesirable.

SUMMARY OF THE INVENTION

The present invention provides a selectively rigidizable and activelysteerable articulatable device. In one aspect, an articulatable deviceis described that includes a flexible inner tube having a first lumen, aflexible outer tube that receives the inner tube, and a multiplicity ofoverlapping, rigidizable scale-like strips. Each scale-like strip iscoupled with the inner tube and positioned between the inner and outertubes. Of particular note, the overlapping strips are actuatable betweena non-rigidized state in which overlapping strips are slideable relativeto one another and a rigidized state in which overlapping strips are notslideable relative to one another.

In various preferred embodiments, the scale-like strips are arranged ina multiplicity of independently actuatable groups. In other embodiments,each strip may be individually addressable and actuatable. A variety ofmeans may be used to actuate the strips from the non-rigidized state tothe rigidized state. Generally, selected overlapping strips arerigidized by selectively controlling frictional forces between adjacentoverlapping strips. By way of example, various electrostatic orpneumatic systems may be utilized to force overlapping strips togetherand increase the friction therebetween.

In another aspect, a method is disclosed for selectively rigidizing anarticulatable device such as that just described. Generally, the methodincludes applying an electric field across selected adjacent ones of theoverlapping scale-like strips. The electric field results in anelectrostatic attraction that forces the selected adjacent ones of theoverlapping strips together thereby increasing the frictional forcesbetween the selected adjacent ones of the overlapping strips such thatthe selected strips are not substantially slideable relative to oneanother. Consequently, the portion of the inner tube adjacent theselected strips becomes rigidized.

In still another aspect, a method for steering an articulatable deviceat a predetermined region along the length of the device is described.Broadly, the method involves selectively rigidizing a portion of thedevice diametrically adjacent the predetermined region and elevating thepressure within an inner lumen of the device such that a portion of thedevice diametrically opposite the rigidized portion expands while therigidized portion is substantially prevented from expanding. As aresult, the device is curved around the rigidized portion therebysteering the device.

These and other features and advantages of the present invention will bedescribed in the following description of the invention and associatedfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and the advantages thereof may best be understood byreference to the following description taken in conjunction with theaccompanying drawings in which:

FIG. 1 illustrates a perspective view of a portion of an examplearticulatable device in accordance with an embodiment of the presentinvention.

FIGS. 2A and 2B illustrate diametric and axial cross-sectional views,respectively, of a portion of the articulatable device of FIG. 1.

FIG. 3A illustrates a number of integrally formed scale-like strips inaccordance with an embodiment of the present invention.

FIG. 3B illustrates the scale-like strips of FIG. 3A wrappedcircumferentially around an inner tube in accordance with an embodimentof the present invention.

FIG. 3C illustrates the scale-like strips of FIG. 3A wrapped helicallyaround an inner tube in accordance with an embodiment of the presentinvention.

FIG. 4A illustrates a portion of the articulatable device of FIG. 1 in anon-activated contracted state in accordance with an embodiment of thepresent invention.

FIG. 4B illustrates a portion of the articulatable device of FIG. 1 in anon-activated elongated state in accordance with an embodiment of thepresent invention.

FIG. 4C illustrates a portion of the articulatable device of FIG. 1 in arigidized elongated state in accordance with an embodiment of thepresent invention.

FIG. 5A illustrates a portion of the inner tube of the articulatabledevice of FIG. 1 having scale-like strips in a non-rigidized state inaccordance with an embodiment of the present invention.

FIG. 5B illustrates the scale-like strips of FIG. 5A in a rigidizedstate in accordance with an embodiment of the present invention.

FIG. 6A illustrates a diagrammatic cross-section of an examplearticulatable device having a number of independently controllablecircumferential subvolumes in accordance with an embodiment of thepresent invention.

FIG. 6B illustrates an axial cross-section of an example articulatabledevice having a number of independently controllable longitudinalsubvolumes in accordance with an embodiment of the present invention.

FIG. 7A illustrates an axial cross-section of a portion of an examplearticulatable device that utilizes electrostatic clamping in anon-activated state in accordance with an embodiment of the presentinvention.

FIG. 7B illustrates the device of FIG. 6A in an electrically activatedclamped rigid state.

FIG. 8 shows a flowchart illustrating a process for actively steeringand advancing an articulatable device in accordance with an embodimentof the present invention.

FIGS. 9A-9C illustrate various steps in the process of FIG. 8.

In the drawings, like reference numerals are sometimes used to designatelike structural elements. It should also be appreciated that thedepictions in the figures are diagrammatic and not to scale.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

The present invention generally relates to articulatable devices andtools and, particularly, to articulatable devices that are selectivelyrigidizable and/or actively steerable. As will be apparent from thefollowing description, the ability to actively and selectively rigidizeall or portions of an articulatable device affords many advantages andenables a variety of previously unfeasible applications. Morespecifically, such an articulatable device may be rigidized along adesired length of the device and at a specific region around thecircumference of the device. The rigidized portion is prevented orsignificantly inhibited from elongating or contracting while otherportions of the device, including the portion diametrically opposite therigidized portion, remain longitudinally flexible, which can helpfacilitate bending and thus steering of the device around the rigidizedportion. Additionally, upon full deployment of the articulatable device,the entire rigidizable portion of the device may be rigidized therebyproviding a firm platform from which to perform various proceduresand/or along which to pass various other tools and instruments. Ofparticular note, the articulatable devices described herein maygenerally be rigidized in any configuration; that is, the devices may berigidized to maintain virtually any shape, however convoluted, that thedevice was in prior to rigidization.

A variety of methods and structures for selectively rigidizing variousarticulatable devices will be described below. Broadly, the inventionutilizes control over the frictional forces between overlapping elementsarranged on the device to selectively prevent or inhibit movementbetween adjacent overlapping elements thereby controllably andselectively rigidizing a desired portion of the device. In particularembodiments, the aforementioned elements take the form of thinscale-like strips arranged around the circumference and along the lengthof a flexible tube. A variety of means are described for increasing thefriction between these scale-like strips including, by way of example,electrostatic attraction as well as various mechanical mechanisms suchas compressing overlapping strips together via pneumatic systems.

Various aspects of the present invention are described in detail withreference to various example embodiments as illustrated in theaccompanying drawings. In the following description, numerous specificdetails are set forth in order to provide a thorough understanding ofthe present invention. It will be apparent, however, to one skilled inthe art, that the present invention may be practiced without some or allof these specific details. In other instances, well known process stepsand/or structures have not been described in detail in order to notunnecessarily obscure the present invention.

Referring initially to FIG. 1, an example articulatable device 100(hereinafter also referred to as “articulatable tool”) will bedescribed. Articulatable device 100 generally resembles a snake-like ortentacle-like arm and may be configured to use tools and/or otherinstruments. In another embodiment, articulatable device 100 is equippedwith a camera, video camera, thermal imaging system, scope, and/orvarious sensors (e.g., gas, pressure, temperature) among other devices.In some embodiments, articulatable device 100 may be configured as aguide, sleeve or outer skin for use with other tools and various otherdevices. By way of example, a tool or other device may be insertedwithin the central lumen 120 of articulatable device 100 such thatdevice 100 surrounds the respective device and can be used selectivelyrigidize portions of the device. In some of these embodiments,articulatable device 100 may serve as a guide to steer and navigate therespective device. The length, width (diameter) and cross-section ofarticulatable device 100 may vary widely according to the needs of aparticular application. By way of example, lengths on the order ofcentimeters to meters are suitable in many embodiments.

As shown by cross-section 101 illustrated in FIG. 1, articulatabledevice 100 generally includes an inner tube 102, an outer tube 104 and anumber of actuatable elements 106 arranged in an intermediate volume 108between an outer surface 103 of inner tube 102 and an inner surface 105of outer tube 104. In various embodiments, actuatable elements 106 takethe form of scale-like strips that are arranged such that adjacentstrips overlap one another. More specifically, the scale-like strips 106are arranged such that at least a portion of a given strip overlaps atleast a portion of an adjacent strip. In the following description ofexample embodiments, actuatable elements 106 may generally be referredto as scale-like strips 106. However, this is not intended tospecifically limit the geometries of the actuatable elements for allembodiments. Articulatable device 100 may have tens, hundreds orthousands (or more) of individual scale-like strips 106.

Inner tube 102 may be regarded as a deformable structure in that innertube 102 is flexible in at least a longitudinal direction along thelength of the inner tube. More specifically, in various embodiments,inner tube 102 is able to longitudinally contract or elongate but isconstrained from expanding radially. Inner tube 102 may be formed from anumber of different materials. By way of example, inner tube 102 may beformed from silicone, polyurethane, as well as a variety of othersuitable elastic materials. Additionally, in some preferred embodiments,the wall 110 of inner tube 102 may have sufficient axial strength so asto inhibit or prevent buckling of inner tube 102 when inner tube 102 isbent or curved such as during use. Generally, a suitable inner tube wallthickness will depend upon many factors including the material andgeometry of the inner tube, including the size of inner lumen 120.Alternatively, inner lumen 120 can be pressurized with a fluid such asair or some other gas or liquid to prevent buckling when subjected tocompressive loads. For other embodiments that don't rely on internalpressure to maintain their cross-section, thicker wall thicknesses maybe desirable.

In embodiments in which inner tube 102 is formed from a material, suchas polyurethane, that is radially expandable, a number ofcircumferential constraints may be provided at spaced locations alongthe length of the inner tube 102. The circumferential constraints arearranged to inhibit or prevent radial expansion of the inner tube 102beyond a desired diameter. The circumferential constraints are generallyformed from rings of inelastic material and may be fixed with a suitableadhesive or other means with the outer surface 103 of the inner tube 102such that the circumferential constraints are maintained at desiredpositions along the length of the inner tube 102 whether the inner tubeis contracted, elongated or in some other equilibrium state. In someembodiments, the actuatable elements or scale-like strips 106 may bearranged over the circumferential constraints.

In the embodiment illustrated in FIG. 1, an outer tube 104 is arrangedaround inner tube 102 such that inner tube 102 and outer tube 104 may beroughly concentric in certain equilibrium and/or nonequilibrium states.Outer tube 104 is also formed from a material that is preferably able toexpand and contract longitudinally along the length of the outer tube.By way of example, a number of elastic materials such as polyurethanemay be suitable for use in forming outer tube 104.

In some embodiments, outer tube 104 may also be radially expandable suchthat the diameter of the outer tube 104 may be varied. By way ofexample, outer tube 104 may be formed from an elastic material thatenables outer tube 104 to radially expand when the pressure withinintermediate volume 108 is raised sufficiently relative to thesurrounding environment. Outer tube 104 may also be formed from anelastic or other flexible material that enables outer tube 104 toradially contract when the pressure within intermediate volume 108 issuitably reduced thereby enabling the inner surface of the outer tube tocontact and compress the scale-like strips 106. Like inner tube 102, thethickness of the wall of the outer tube 104 may vary widely according tothe needs of a particular application as well as according to thematerial and geometry of the outer tube.

Articulatable device 100 includes a tip 114 at a distal end 116 of thedevice. Tip 114 may be configured into virtually any desired shape. Insome embodiments, inner tube 102 and outer tube 104 are connected orcoupled with tip 114 and cooperate with tip 114 to hermetically sealintermediate volume 108. In some embodiments, a hermetically sealedintermediate volume 108 may be controllably inflated and deflated withvarious gases (e.g., air, helium, etc). Additionally, in the illustratedembodiment, tip 114 includes an aperture 118. Aperture 118 isparticularly useful in embodiments in which it is desirable to passtools or instruments through central lumen 120 of articulatable device100 and into or out of aperture 118.

FIGS. 2A and 2B illustrate diametric cross-sectional and axial views,respectively, of a portion of articulatable device 100. FIGS. 2A and 2Bshow one particular arrangement of scale-like strips 106 in more detail.Unlike inner tube 102 and outer tube 104, scale-like strips 106 areformed from a relatively stiff or inelastic material. By way of example,a number of non-expandable plastic or polymeric materials may be used toform scale-like strips 106. Generally, the scale-like strips 106 areformed so as to be bendable but not extendable; that is, the stripsresist tensile strain. In some particular embodiments, scale-like strips106 are formed from thin strips of Mylar or nylon. Although suitablethicknesses may vary, each scale-like strip 106 may have a thickness inthe range of approximately 20 to 60 μm in some particular embodiments.In other embodiments, the strips 106 may be much thicker. Furthermore,in some of the embodiments described below, the strips are formed from adielectric material. Dielectric scale-like strips 106 are particularlyuseful in embodiments in which electrostatic forces are used to rigidizethe strips 106. In some of these electrostatic embodiments, one outersurface 122 of each scale-like strip 106 is metallized or otherwisecoated with a conductive layer. In one particular embodiment, aconductive coating of Aluminum is sputtered, plated or otherwisedeposited or attached to outer surfaces 122 of the scale-like strips106.

In the illustrated embodiment, each scale-like strip 106 is coupled withthe outer surface 103 of inner tube 102. By way of example, eachscale-like strip 106 may be secured to the outer surface 103 of innertube 102 with a suitable adhesive. However, in some alternateembodiments, the scale-like strips may be coupled with the inner surface105 of outer tube 104. Generally, the composition, shape, arrangementand absolute and relative sizes of the scale-like strips 106 may beextremely widely varied. In one embodiment, the scale-like strips 106are sized relative to the spacing between the scale-like strips toensure that there is sufficient surface area overlap between adjacentstrips to allow clamping (rigidization), even when the inner tube 102undergoes maximum strain. Generally, scale-like strips with smallerabsolute size allow for more intricate variations in strain, subject tothe constraint that the frictional force generated in the overlappingareas must remain sufficiently large to resist the tensile stressresulting from applied loads. In one embodiment, if the scale-likestrips are relatively short, the thickness of each scale-like strip maybe made relatively thinner to allow for more a more bent or curved shapewhen clamped or unclamped (non-rigidized). Additionally, although theillustrated embodiments generally show the scale-like strips as beingrectangular, this is not a requirement in all embodiments. CopendingU.S. patent application Ser. No. 11/078,678 entitled “MechanicalMeta-Materials,” which is hereby incorporated by reference herein forall purposes, describes various embodiments of suitable scale-likestrips and other actuatable elements as well as a few correspondingmethods of use and applications.

In the embodiment illustrated in FIGS. 2A and 2B, the scale-like strips106 are arranged in rows around the circumference of the inner tube 102with portions of the strips from a given row overlapping correspondingportions of the strips from the next immediately adjacent row.Additionally, in the illustrated embodiment, each scale-like strip 106is its own individual (discrete) element; that is, each strip is notintegrally formed with the adjacent strips surrounding it. The strips106 are generally arranged such that they are aligned with the centrallongitudinal axis of the inner tube 102.

In another particular embodiment illustrated in FIGS. 3A and 3B, anumber of scale-like strips 106 are integrally formed from a singlelarger strip or sheet. By way of example, FIG. 3A illustrates an examplerectangular sheet 307. Sheet 307 has been cut so as to form amultiplicity of scale-like strips 306. Of particular note, each cut doesnot proceed entirely across the width of the sheet 307 such that eachstrip 306 remains coupled with the strips 306 adjacent to it via theuncut “root” portion 309. The widths of the strips 306 may varyaccording to the specific application, but in some specific embodiments,each cut is approximately in the range of 3 to 12 mm (roughly 0.125 to0.5 in) from each immediately adjacent cut. In larger embodiments, thewidths of the strips may be on the order of a centimeter or tens ofcentimeters (or larger). The number of strips 306 integrally formed fromeach sheet 307 may also vary widely. In one embodiment, the length ofeach sheet 307 is suitably sized such that it corresponds to thecircumference of the inner tube 302. In this embodiment, the uncut rootportion 309 of each sheet 307 is wrapped around and adhesively securedto the circumference of the inner tube 102 so as to form a ring ofintegrally connected strips 306 as shown in the axial view illustratedin FIG. 3B. In embodiments in which the inner tube is radiallyexpandable, the sheets 307 of scale-like strips 306 may, themselves,serve as circumferential constraints. In another embodiment, longersheets 307 are used. By way of example, in the axial view illustrated inFIG. 3C, a single sheet 307 is helically wound around the inner tube302.

In a non-activated (hereinafter also referred to as “non-actuated” or“non-rigidized”) state, the friction between adjacent scale-like strips106 is relatively negligible thereby allowing adjacent strips to slideover one another with negligible force as shown in FIGS. 4A and 4B,which illustrate a portion of device 100 in contracted and elongatedstates, respectively. By way of example, in some embodiments the deviceis longitudinally collapsible to within a range of approximately 10 to25% of its maximum length. In the non-activated state, inner tube 102 isable to contract and elongate according to the stiffness or elasticityof the inner tube 102. Extrapolating, the stiffness or elasticity of thedevice 100 in the non-activated state is some combination of thestiffnesses of the inner and outer tubes 102 and 104, respectively, andis not significantly affected by the frictional forces between thescale-like strips 106.

However, according to embodiments of the present invention, thefrictional forces between adjacent scale-like strips 106 may beselectively varied. Generally, the frictional forces between adjacentscale-like strips 106 are selectively and controllably varied bycompressing or clamping adjacent overlapping scale-like strips 106. Afew example embodiments for selectively and controllably varying thefrictional forces between adjacent scale-like strips 106 will now bedescribed. FIGS. 5A and 5B illustrate perspective views of a portion ofinner tube 102 having scale-like strips 106 in non-rigidized andrigidized states, respectively (although only a portion inner tube 102is shown as having scale-like strips 106, it should be understood thatthe entire length of inner tube 102 may have the scale-like stripsarranged on it).

In some embodiments, a pneumatic system is utilized to vary the frictionbetween selected scale-like strips 106. More particularly, in oneembodiment, a vacuum source is used to draw vacuum to reduce thepressure (e.g. air pressure) within intermediate volume 108 below thatof the surrounding environment. The reduction in pressure withinintermediate volume 108 has the effect of radially contracting outertube 104. When the pressure is sufficiently reduced, the inner surface105 of outer tube 104 contacts and exerts a radial force inward onvarious outer surfaces 122 of scale-like strips 106. FIG. 4C illustratesthe articulatable device 100 of FIGS. 4A and 4B in such areduced-pressure clamped or activated state. As a result of thecontraction of outer tube 104, the normal force, and hence thefrictional force, between overlapping surfaces of various scale-likestrips 106 is increased. Below a suitable pressure, the increasedfrictional force between overlapping scale-like strips 106 inhibitsrelative movement between them.

As a result of the increased friction, the inelastic overlappingscale-like strips 106 are rigidized, or more specifically, theoverlapping scale-like strips 106 effectively combine to form aninelastic unitary structure that assumes the stiffness of the inelasticmaterial used to form the scale-like strips 106 themselves. Sincerelative movement (e.g., sliding) between the overlapping scale-likestrips 106 is prevented (as long as an applied load isn't too high), theunitary structure formed by the overlapping scale-like strips issubstantially prevented from significant further elongating, contractingor otherwise distorting relative to the arrangement or shape of thescale-like strips 106 prior to rigidization.

Since the overlapping scale-like strips 106 are fixed with the innertube 102, the flexible inner tube 102 is also effectively rigidized. Inthe illustrated embodiment, such a reduction of pressure in the entireintermediate volume 108 would have the effect of rigidizing the entirearticulatable device 100. Moreover, articulatable device 100 may berigidized in virtually any shape or configuration. More specifically,articulatable device 100 may be bent at one or more regions along thelength of the device and subsequently rigidized such that device 100maintains the bent form the device was in prior to rigidization. Such arigidizing ability is useful in a wide assortment of applications. Byway of example, articulatable device 100 can be rigidized such thattools or other instruments can be guided and passed through device 100.

In various embodiments, it is desirable to selectively rigidize or clamponly smaller selected specific portions or regions of articulatabledevice 100. To facilitate this, intermediate volume 108 may be dividedor portioned into a number of subvolumes. By way of example, FIGS. 6Aand 6B illustrate diametric and axial cross-sections, respectively, ofexample articulatable devices 600 that utilize pneumatic (e.g., vacuum)systems to rigidize selected regions adjacent independently controllablesubvolumes. In the embodiment illustrated in FIG. 6A, intermediatevolume 108 is divided into four independently controllablecircumferential subvolumes, sections or channels 630. Such channels 630may be formed, by way of example, by connecting longitudinal segments ofthe outer surface 103 of inner tube 102 with the inner surface 105 ofouter tube 104. In the illustrated embodiment, channel walls 632interconnect the inner and outer tubes 102 and 104, respectively. In analternate embodiment, portions of the inner tube 102 itself may beadhesively secured or welded to the outer tube 104 to form the channels630. Although only four channels 630 are shown in FIG. 6A, it should benoted that the number of channels 630 may vary according to the needs ofa particular application. Generally, in such embodiments that utilizevacuum to rigidize the scale-like strips, the number of channels 630 ata given cross-section dictates the number of degrees of freedom, or moreparticularly, the number of distinct directions of bending the device iscapable of at that cross-section. By way of example, each distinct axisthe device is able to bend around provides two degrees of freedom. Eachchannel 630 may be connected with its own associated vacuum line. Inthis way, the pressure in only one or more selected channels 630 may bereduced so as to rigidize the scale-like strips 106 in only the selectedchannel(s), and thereby only the portion of the inner tube 102 adjacentthe selected channel(s). It should be noted that rigidizing scale-likestrips 106 in two or more channels 634 at a given diametriccross-section can provide additional axes of rotation and hence, moredegrees of freedom.

Intermediate volume 108 may also be divided into subvolumes along thelength of the device as illustrated by the longitudinal cross-section ofFIG. 6B. In the illustrated embodiment, the intermediate volume 108 islongitudinally divided into four longitudinal sections 634 by sectionwalls 636. Although only four longitudinal sections 634 are shown, itshould be noted that the number of longitudinal sections 634 may bewidely varied based on the needs of a particular application. Generally,in such embodiments that utilize vacuum to rigidize the scale-likestrips, the number of longitudinal sections 634 dictates the number ofseparately rigidizable longitudinal portions of articulatable device600. More particularly, since each section 634 may be rigidizedindependently of the other sections, a portion of the device that hasalready being navigated through a turn may be rigidized while otherportions of the device remain flexible. Moreover, in some embodiments itmay be desirable to incorporate a number of independently controllablecircumferential sections (such as channels 630 described with referenceto FIG. 6A) within each longitudinal section 634, thereby enabling evenmore selective control over which portions of the device are rigidized.

In various alternate embodiments, the scale-like strips 106 ofarticulatable device 100 may be clamped and rigidized via other means.In one alternate embodiment, electrostatic forces are utilized to clampor rigidize selected scale-like strips 106. In these embodiments, thescale-like strips 106 are formed from a dielectric material. In someparticular embodiments, one outer surface 122 of each scale-like strip106 is metallized or coated with some other conductive layer. By way ofexample, outer surfaces of Mylar or nylon strips may be metallized witha thin film of aluminum.

In an example electrostatic embodiment, an electrostatic potential isapplied to selected strips and/or to associated electrodes on the innerand/or outer tubes 102 and 104. When a sufficient electrostaticpotential is applied, an electric field is created between adjacentoverlapping scale-like strips that forces the strips together therebyincreasing the frictional force between them and eventually rigidizingadjacent overlapping scale-like strips.

FIG. 7A illustrates a portion of an axial cross-section of anarticulatable device 700 having electrically actuatable scale-likestrips 706. In the illustrated embodiment, each electrically actuatablescale-like strip 706 has an associated electrode 707 attached to thewall of the inner tube 102 adjacent the particular scale-like strip.FIG. 7B illustrates the device of FIG. 7A while in a clamped orrigidized state. In the embodiment illustrated in FIG. 7B, outerconductive surfaces 722 of selected scale-like strips 706 are groundedwhile associated electrodes 707 adjacent the selected scale-like stripsare biased to a positive voltage +V. By way of example, a positivevoltage in the range of 500 to 5000 Volts has been shown to work well insome embodiments.

In an alternate embodiment, electrodes 707 are not required. In thisembodiment, the outer surfaces of adjacent overlapping scale-like strips706 are biased to different voltages. By way of example, the outerconductive surfaces of a first row of strips 706 may be biased to avoltage V+ while the outer conductive surfaces of an immediatelyadjacent second row of strips 706 may be grounded or biased to anegative voltage V− thereby clamping the adjacent overlapping strips.This pattern may be repeated such that a third row of strips 706immediately adjacent the second row is again biased to +V.

In still another embodiment, addressable electrodes 707 are alsopositioned on the outer tube 704. In this embodiment, the scale-likestrips 706 may be entirely formed from a dielectric material and do notinclude conductive surfaces. Rather, when selected scale-like strips 706are to be clamped, opposing voltages may be applied to the electrodes707 on the inner and outer tubes 702 and 704, respectively. By way ofexample, selected electrodes 707 on the inner tube 702 may be biased toa positive voltage V+ while diametrically adjacent associated electrodes707 on the outer tube 704 are grounded or biased to a negative voltageV− thereby generating an electric field across the associated scale-likestrips 706 in between the biased electrodes 707.

More details of electrostatic clamping mechanisms can be found incopending U.S. patent application Ser. No. 11/078,678 entitled“Mechanical Meta-Materials,” which is incorporated by reference hereinfor all purposes.

In various embodiments, both the scale-like strips 706 themselves aswell as any associated electrodes are individually addressable therebypermitting selective rigidization control at the granularity of thescale-like strips 706 themselves. In other embodiments, it may besufficient to address a plurality of scale-like strips 706 and/or theassociated electrodes 707 at a group level thereby rigidizing a group ofthe strips simultaneously. In some embodiments individual wires may beused to electrically connect the scale-like strips 706 with a controllercoupled with the device. Such wires may be routed through intermediatevolume 708 and/or the central lumen 720. Alternately, the scale-likestrips 706 and electrodes 707 may be electrically connected with thecontroller via electric traces that may be printed or otherwisedeposited onto the outer surface 703 of inner tube 702 itself.Additionally, the electrodes 707 themselves may also be printed onto theassociated surface of the inner 702 or outer tube 704. By way ofexample, such electric traces may be formed of graphite deposited ontothe respective surface.

In still other embodiments, other means of altering the frictionalforces between overlapping scale-like strips 106 may be used. By way ofexample, in some embodiments, magnetic clamping may be used to rigidizethe scale-like strips 106. Additionally, it will be appreciated that anyof the described means of altering the frictional forces betweenoverlapping scale-like strips 106 are tunable; that is, the frictionalforces, and hence the degree of rigidization, may be finely controlled.Generally, the precision of tunable control will depend on the number ofscale-like strips 106 and the granularity of addressing used to activateor rigidize the scale-like strips.

While the foregoing embodiments were described with reference tospecific arrangements of scale-like strips 106, it should be noted thatselective rigidization may be practiced with a wide assortment ofarrangements of scale-like strips having varying sizes and shapes. Byway of example, thus far the embodiments have shown overlap ofscale-like strips in a regular pattern in a single direction. That is,the actuatable elements, strips or scales 106 have generally beenarranged in rows. Such arrangements are well suited for materials wherethe external loads are applied in one direction (such as axial loads).However, the arrangement of the scale-like strips is not limited to sucha simple arrangement and other arrangements are contemplated. By way ofexample, the scale-like strips may be arranged such that there isoverlap between adjacent strips in all or a number of differentdirections. Such an arrangement of scale-like strips allows thearticulatable device to respond as desired to loads in a multitude ofdirections as well as to bending moments applied to the device.

Additionally, as described above, the width and orientation of thestrips 106 may also be widely varied. In one embodiment, the scale-likestrips are implemented with an aspect ratio (length vs. width) that isrelatively low. By way of example, an aspect ratio between about 1 andabout 5 is suitable in many embodiments. To maintain multi-dimensionalcontrol of the stiffness, the scale-like strips may overlap in bothlongitudinal and circumferential directions. Other aspect ratios mayalso be employed. In another embodiment, narrow scale-like strips (ahigh aspect ratio) are utilized.

Furthermore, while the aforementioned embodiments were described asincluding both an inner and an outer tube, this is not a requirement inall embodiments. By way of example, in some embodiments an outer tube isnot included. In embodiments in which electrostatic forces are used torigidize the scale-like strips, the outer surface of the strips may beinsulating so as to not create an electrical pathway to the surroundingenvironment. In other embodiments, an inner tube is not included. Inthese embodiments, the scale-like strips are coupled with the innersurface of the tube.

In still other alternate embodiments, the outer tube 104 and/or innertube 102 may not take the form of solid-walled tubes but, rather,perforated tubular or cylindrical structures. By way of example, thewalls of one or both of the tubes may resemble a braided, woven or “fishnet” design. It should also be recognized that the cross-sections of theinner and outer tubes need not be circular in all embodiments. By way ofexample, oval or elliptical cross-sections may be suitable in someparticular applications. Additionally, the inner and outer tubes neednot be closed form in all embodiments; that is, a diametriccross-section of the tube wall may form a “c” shape, “u” shape or otherdesired shape in other embodiments.

Various applications and methods of use of an articulatable device suchas any of those described above will now be described. In one aspect,selective rigidization is utilized to steer an articulatable device. Byway of example, FIG. 8 shows a flowchart illustrating one exampleprocess for actively steering an articulatable device. In oneembodiment, an articulatable device 900 having scale-like strips (notshown) such as any of those described above is provided in a contractedstate. In one particular embodiment, the scale-like strips andassociated tube(s) are telescopically contracted such that some of thestrips and portions of the tube are contracted within each other similarto an extendable telescope.

At 802, the distal end 916 of the articulatable device is extended fromthe remaining contracted portion as illustrated in FIG. 9A. In aparticular embodiment, the distal end of the articulatable device isarranged to extend telescopically from the remaining contracted portionof the device 900. However, in some alternate embodiments, the proximalend 917 of the articulatable device 900 is the first to elongate. Inthese embodiments, the contracted portion is advanced and the distal end916 of the device may be the last portion to elongate.

The articulatable device may be extended with any suitable means. By wayof example, in various embodiments the pressure within the inner centrallumen of the device can be increased so as to elongate a desired portionof the device. In various embodiments, a specific selected region orportion of the device can be elongated by increasing the central lumenpressure and rigidizing the scale-like strips not associated with thespecific portion such that the selected portion is free tolongitudinally expand while other portions of the device remain rigidand unable to elongate.

At 804, a selected region 950 of the extended portion of the device isrigidized to facilitate steering of the device. More particularly, thearticulatable device may be rigidized at a specific region along thelength of the device and along a specific portion of the circumferenceof the device. The specific rigidized region 950 may be rigidized withany suitable means such as any of those described above. At 806, thedevice is bent around the rigidized region thereby turning or steeringthe device around the rigidized region as illustrated in FIG. 9B. In onespecific embodiment, the device is steered around the rigidized portionsby increasing the pressure within the central lumen. Increasing thepressure within the central lumen has the effect of expandingnon-rigidized regions of the inner tube including the non-rigidizedregion diametrically opposite the selected rigidized region. As therigidized region is longitudinally constrained and the non-rigidizedregion is permitted to expand under the force generated by the pressurewithin the central lumen, the device is actively steered around therigidized region. In the way, rigidization itself is used in conjunctionwith elongation to steer the device.

In an alternate embodiment, the distal end 916 of the articulatabledevice 900 may be steered via other means. By way of example, the distalend 916 of the articulatable device 900 may be equipped with steeringcables (hereinafter also “wires,” “steering wires,” or “tensile wires”).The steering cables may run the length of the device, attached at thedistal tip 916, and operated at the proximal end using associatedactuators or manual means. In embodiments in which actuators areutilized, each cable may be coupled with an associated actuatorconfigured to shorten or lengthen the cable. Steering cables andactuators are well known in the art and as such will not be described indetail here. The articulatable device may be bent at any point along itslength by making rigid all but the region around which it is desired tobend the device, and then pulling on the cable or cables correspondingto the direction and magnitude of the desired bend. In variousembodiments, articulatable device 900 may be equipped with three suchsteering cables all coupled with the distal end 916 of the device. Theuse of three such cables enables three-dimensional steering of thedistal end 916. However, while three cables are used in a preferredembodiment, in other embodiments the articulatable device may beequipped with two, four or even more cables thereby enabling finercontrol over the steering of the distal end 916.

The device 900 may then be further extended or advanced at 808 to reacha desired destination. In a particularly useful embodiment, thescale-like strips are either individually addressable and actuatable orat least addressable or actuatable in sufficiently small groups toenable a user (or a computer or circuit controlled by the user) to havefine control over where and when specific selected regions of the deviceare rigidized. In one embodiment, after a turn is made, the device isfurther advanced using a locomotion scheme that may resemble arectilinear locomotion scheme used by some snake species. Moreparticularly, while the proximal end of the articulatable device ispushed (or while the device is elongated telescopically) the scale-likestrips at the selected rigidized region of the device at the turn areunclamped or unrigidized such that they may be advanced. Concurrently,the proximal scale-like strips 906 immediately adjacent the formerlyrigidized strips are then rigidized. In this way the articulatabledevice may be advanced while the absolute location of the bend or turnin the device remains unchanged.

At 810 it is determined whether or not the destination has been reached.If the destination is reached, the process may end here. However, onceat a desired destination, the entire rigidizable length of thearticulatable device or portions thereof may be rigidized using any ofthe methods described herein. Rigidizing the articulatable device allowsthe device to serve as a rigid platform or guide for passing tools,instruments and other things through the central lumen of the device andin some embodiments out of the distal end of the device. Additionally,in some embodiments an intermediate volume between the inner tube andouter tube is pressurized to expand the outer tube. By way of example,it may be desirable to expand the entire outer tube or portions thereofto increase the rigidity of the device and reduce the propensity forbuckling, or such that the outer surface of the device contacts thewalls of, for example, a surrounding enclosure such as a tube or pipe.This can serve to anchor the device within the surrounding enclosure.

If, however, the target destination has not been reached because, forexample, more turns are required, then the process returns to 804.Recalling that the articulatable device can be advanced while theabsolute location of a bend or turn remains fixed, the distal end of thedevice can be actively turned numerous times while locomotion is used toadvance the device such that bends that have already been made remain inthe corresponding original absolute locations. Moreover, it should benoted that the steering cables coupled with the distal end of the devicecan control the movement/steering of multiple articulations byrigidizing all but the articulation that is being moved. With such ascheme only one articulation may be moved at a time, but numerousarticulations can be controlled with just the common set of cablescoupled with the distal end of the articulatable device. In one exampleembodiment, a computer controller is used to sequentially actuate (e.g.,via electrostatic or other suitable means) the scale-like strips througheach articulation in small discrete steps. Furthermore, by increasingthe rate of the sequential actuations and by reducing the size of thescale-like strips, the discrete steps become smoother and theadvancement of the articulatable device more closely resemblessnake-like motion. Preferably, the rate of advancement of the device iscarefully controlled (e.g., by the user or with computer controlledmechanisms) such that the timing of the sequence of actuations coincideswith the rate of advancement of the device. In this way, thearticulatable device can advance smoothly using movements that wouldconventionally require simultaneous movement of the articulations withindependent actuators. This enables a user to actively steer the distalend of the articulatable device all of the way to the targetdestination. FIG. 9C illustrates articulatable device 900 after a secondturn. During the second turn, all but the portion of the device 900 atthe second turn may be rigidized.

Additionally, it should be noted that in embodiments in which steeringcables are used to steer or guide the device, only three total cablesare required for three-dimensional motion and for virtually any numberof articulations or turns along the length of the articulatable device.More specifically, by pulling on one of the cables a torque is exertedon the body of the device, which results in bending at the articulationswhich are not clamped or rigidized. With this technique the device canbe bent into complex shapes using a limited number of actuators. Incontrast, those of skill in the art will appreciate that, generally,conventional articulatable devices require cables or other actuators oneach segment or joint to permit multiple articulations. As such, thenumber of cables and/or actuators required dramatically increases withthe degrees of freedom desired for conventional devices. However, theability to selectively rigidize specific small regions of thearticulatable device according to embodiments of the present inventionpermits multiple articulations in three dimensions along the length ofthe device with only three cables (or two cables for multiplearticulations in two dimensions).

The described articulatable devices may find use in numerousapplications. By way of example, the described articulatable devices areparticularly suitable for use in various surveillance, inspection andmaintenance applications. By way of example, in various examplesurveillance applications, the articulatable device may be equipped witha camera, video camera, thermal imaging system or some other imagingsystem at the distal end of the device. In some embodiments, a user suchas a law enforcement officer or military personnel may secretly positionthe device in proximity to a suspect, foe or other party to be surveyed.The device may then be either manually or electronically (via a computercontroller), and even remotely, navigated via the described methods intoa window or hole in a wall or ceiling or even through an air duct orpipe into a room where the surveyed party is located. The articulatabledevice may also be equipped with audio recording equipment and/or even aweapon. In some embodiments, a gas such as tear gas may be passedthrough the central lumen and released out of the aperture at the distalend of the device and into the room. In still other embodiments, thedevice may also be equipped with tools such as wire cutters and pliersfor use in disarming a bomb.

In other embodiments, an articulatable device may be utilized forinspection or maintenance purposes. By way of example, the device may beequipped with a light and/or various tools to inspect a mechanical orelectrical system, diagnose a problem and/or fix or repair the problemwith the tools under guidance by a user who may be viewing remotely viaa video camera at the distal end of the device. The device is especiallysuited for use in inspected pipes and other tubular structures. Thedevice may also be used in exploratory purposes such as in cave systems(even underwater) or within wreckage (to search for trapped victims)where it is unsafe for humans to venture. The articulatable device isespecially useful in these embodiments as it is lightweight andtherefore may be able to extend much longer than conventional deviceswithout buckling or breaking.

In various embodiments, the articulatable devices are reconfigurable;that is, various tools, instruments or other devices may be passedthrough the central lumen of the device and exchanged with other toolsas needed thereby increasing the applicability of the device.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the invention.However, it will be apparent to one skilled in the art that the specificdetails are not required in order to practice the invention. Thus, theforegoing descriptions of specific embodiments of the present inventionare presented for purposes of illustration and description. They are notintended to be exhaustive or to limit the invention to the precise formsdisclosed. It will be apparent to one of ordinary skill in the art thatmany modifications and variations are possible in view of the aboveteachings.

The embodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, to therebyenable others skilled in the art to best utilize the invention andvarious embodiments with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

What is claimed is:
 1. An articulatable device, comprising: a flexibleinner tube having a first lumen; a flexible outer tube that receives theinner tube; a multiplicity of overlapping, rigidizable scale-like stripseach coupled with the inner tube and positioned between the inner andouter tubes, the strips being actuatable between a non-rigidized statein which overlapping strips are slideable relative to one another and arigidized state in which overlapping strips are not slideable relativeto one another; and a vacuum source arranged to selectively apply avacuum to a region between a portion of the inner tube and acorresponding portion of the outer tube, wherein the adjacentoverlapping strips are arranged to be pressed together under theinfluence of the vacuum thereby substantially increasing the frictionalforces between the adjacent overlapping strips to thereby help rigidizea portion of the articulatable device.
 2. The articulatable device asrecited in claim 1, wherein the overlapping scale-like strips are formedfrom an substantially inelastic material and wherein adjacentoverlapping ones of the inelastic scale-like strips.
 3. Thearticulatable device as recited in claim 2, wherein the scale-likestrips are arranged in a multiplicity of independently actuatablegroups.
 4. The articulatable device as recited in claim 3, wherein atleast some of the independently actuatable groups of scale-like stripsare circumferentially separated such that one side of a section of theinner tube may be selectively rigidized while an opposing side of theinner tube is not rigidized to facilitate bending of the articulatabledevice.
 5. The articulatable device as recited in claim 3, wherein atleast some of independently actuatable groups of scale-like strips arelongitudinally separated such that longitudinally distinct sections ofthe inner tube may be selectively rigidized.
 6. An articulatable devicecomprising: a flexible inner tube having a first lumen; a flexible outertube that receives the inner tube; and a multiplicity of overlapping,rigidizable scale-like strips each coupled with the inner tube andpositioned between the inner and outer tubes, the strips beingactuatable between a non-rigidized state in which overlapping strips areslideable relative to one another and a rigidized state in whichoverlapping strips are not slideable relative to one another; whereinthe overlapping scale-like strips are formed from an substantiallyinelastic material and wherein adjacent overlapping ones of theinelastic scale-like strips are actable between the rigidized state andthe non-rigidized state by selectively controlling frictional forcesbetween the adjacent overlapping ones of the inelastic scale-likestrips; and wherein the inner tube is radially constrained and whereinthe outer tube is radially expandable.
 7. The articulatable device asrecited in claim 1, wherein an intermediate volume between the inner andouter tubes is divided into at least two subvolumes and wherein thepressure in each of the subvolumes can be independently controlled. 8.The articulatable device as recited in claim 7, wherein the intermediatevolume is divided angularly such that at least two subvolumes extendthrough at least one diametric cross-section of the device therebyenabling the device to be rigidized at least two different regionsaround the circumference of the inner tube.
 9. The articulatable deviceas recited in claim 7, wherein the intermediate volume is dividedlongitudinally such that at least two subvolumes extend through at leastone longitudinal cross-section of the device enabling the device to berigidized at least two different regions along the length of the device.10. The articulatable device as recited in claim 1, further comprisingan electrical source, wherein an electrostatic force is additionallyused to press adjacent overlapping strips together thereby substantiallyincreasing the frictional forces between the adjacent overlappingstrips.
 11. The articulatable device as recited in claim 10, whereineach strip comprises a dielectric material having a conductive coatingon a first surface thereof, and wherein the electrical source isarranged to selectively apply an electric field across selected ones ofthe overlapping strips.
 12. The articulatable device as recited in claim10, wherein one or both of the inner and outer tubes include electrodesand wherein the electrical source is arranged to selectively apply anelectrostatic potential to selected ones of the electrodes therebygenerating an electric field across associated ones of the overlappingstrips.
 13. The articulatable device as recited in claim 1, wherein eachof the strips has a thickness in the range of approximately 20-60 μm.14. The articulatable device as recited in claim 1, wherein the innertube is elastic, the device further comprising a multiplicity of radialconstraints each arranged around a different circumference of the innertube so as to substantially prevent the inner tube from expanding beyonda predetermined diameter and such that the inner tube is capable ofexpanding longitudinally.
 15. The articulatable device as recited inclaim 14, wherein ones of the scale-like strips serve as radialconstraints.
 16. The articulatable device as recited in claim 1, whereinthe device is longitudinally collapsible to within a range ofapproximately 10 to 25% of its maximum length.
 17. A method ofselectively rigidizing an articulatable device that includes a flexibleinner tube having a first lumen, a flexible outer tube that receives theinner tube and a multiplicity of overlapping, rigidizable scale-likestrips positioned between the inner tube and the outer tube, the methodcomprising: applying a vacuum to a region between a portion of the innertube and a corresponding portion of the outer tube such that adjacentoverlapping strips are pressed together under the influence of thevacuum thereby substantially increasing the frictional forces betweenthe adjacent overlapping strips to thereby help rigidize a portion ofthe articulatable device.
 18. The method of claim 17, further comprisingapplying an electric field across selected adjacent ones of theoverlapping scale-like strips, the electric field resulting in anelectrostatic attraction that forces the selected adjacent ones of theoverlapping strips together thereby increasing the frictional forcesbetween the selected adjacent ones of the overlapping strips such thatthe selected strips are not substantially slideable relative to oneanother thereby rigidizing a portion of the inner tube adjacent theselected strips.
 19. The method as recited in claim 18, wherein eachstrip comprises a dielectric material having a conductive coating on afirst surface thereof, and wherein an electrical source is arranged toapply an electrostatic potential to the selected ones of the overlappingstrips thereby generating the electric field across associated ones ofthe overlapping strips.
 20. The method as recited in claim 18, whereinone or both of the inner and outer tubes include electrodes and whereinan electrical source is arranged to selectively apply an electrostaticpotential to selected ones of the electrodes thereby generating theelectric field across associated ones of the overlapping strips.